SEOUL, Oct. 28 (Yonhap) -- The South Korean military's Patriot Advanced Capability-2 (PAC-2) system has a success rate of less than 40 percent in intercepting ballistic missiles, government sources said Sunday.

Due to the noticeable inefficiency in deterring North Korean missiles, the PAC-2 system can only be useful in intercepting airplanes, prompting the South's military to rush to introduce the more advanced PAC-3 system, said the sources.

PAC-2 has been deployed to counter increasing threats from the North's low-flying, short- and medium-range missiles, as part of Seoul's plan to build an independent theater missile defense shield, dubbed the Korean Air and Missile defense (KAMD) network system.

"The Korea Institute for Defense Analyses and the Missile Defense Agency of the U.S. have just concluded a joint study on the KAMD and found that the PAC-2 system has an interception success rate of below 40 percent," said a ranking government official.

"A variety of simulations have concluded that in order to raise the interception rate to above 70 percent, the (South Korean) military has to move to the PAC-3 system."

South Korea has bought 48 PAC-2 systems, including launchers, from Germany at a cost of 1 trillion won (US$909 million) but the PAC-2 launchers can't be used for the PAC-3 system.

Another government source said, "The core computer system in PAC-2 is superannuated. The system has to be diverted for interception of fighters."

At the Security Consultative Meeting (SCM) in Washington last week, South Korean Defense Minister Kim Kwan-jin said that his government will push to build the PAC-3 system. In order to strengthen the total missile system, Kim also stressed South Korea would establish a "kill chain" to detect, target and destroy North Korean ballistic missiles, which are capable of hitting South Korea, Japan and Guam.

Military officials said the PAC-3 and kill chain systems will be pushed in close coordination, forecasting that the PAC-3 system will be introduced starting in 2014.

In a related development, Seoul's defense ministry has strongly denied that South Korea could participate in the U.S. missile defense system, saying that building the KAMD never means participating in U.S. efforts to build a multi-layer defense system.

U.S. Defense Secretary Leon Panetta said Wednesday after the SCM talks with Kim that Washington is still in consultations with Seoul over its future role in a regional missile defense system, raising speculations Seoul could take part in the U.S. missile defense system.